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The brain and eyes, for example, can be significantly impacted by mutations in this gene and cause disorders such as Microphthalmia and Holoprosencephaly. [39] Microphthalmia is a condition that affects the eyes, which results in small, underdeveloped tissues in one or both eyes. [ 39 ]
Rhodopsin, also known as visual purple, is a protein encoded by the RHO gene [5] and a G-protein-coupled receptor (GPCR). It is a light-sensitive receptor protein that triggers visual phototransduction in rod cells. Rhodopsin mediates dim light vision and thus is extremely sensitive to light. [6]
The seven transmembrane α-helical domains in opsins are connected by three extra-cellular and three cytoplasmic loops. Along the α-helices and the loops, many amino acid residues are highly conserved between all opsin groups, indicating that they serve important functions and thus are called functionally conserved residues.
[12] [13] Nucleotide sequencing of opsin genes suggests that the genetic divergence between New World primate opsin alleles (2.6%) is considerably smaller than the divergence between Old World primate genes (6.1%). [11] Hence, the New World primate color vision alleles are likely to have arisen after Old World gene duplication. [4]
Leber's hereditary optic neuropathy (LHON) is a mitochondrially inherited (transmitted from mother to offspring) degeneration of retinal ganglion cells (RGCs) and their axons that leads to an acute or subacute loss of central vision; it predominantly affects adult males, and onset is more likely in younger adults.
Whether the eye evolved once or many times depends on the definition of an eye. All eyed animals share much of the genetic machinery for eye development. This suggests that the ancestor of eyed animals had some form of light-sensitive machinery – even if it was not a dedicated optical organ.
The Notch/Lin-12/Glp-1 receptor family [23] was found to be involved in the specification of cell fates during development in Drosophila and C. elegans. [24] The intracellular domain of Notch forms a complex with CBF1 and Mastermind to activate transcription of target genes. The structure of the complex has been determined.
Optogenetics is a biological technique to control the activity of neurons or other cell types with light.This is achieved by expression of light-sensitive ion channels, pumps or enzymes specifically in the target cells.